1 /*
2 * Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 #include "modules/rtp_rtcp/include/remote_ntp_time_estimator.h"
12
13 #include "absl/types/optional.h"
14 #include "modules/rtp_rtcp/source/time_util.h"
15 #include "system_wrappers/include/clock.h"
16 #include "system_wrappers/include/ntp_time.h"
17 #include "test/gmock.h"
18 #include "test/gtest.h"
19
20 namespace webrtc {
21 namespace {
22
23 constexpr TimeDelta kTestRtt = TimeDelta::Millis(10);
24 constexpr Timestamp kLocalClockInitialTime = Timestamp::Millis(123);
25 constexpr Timestamp kRemoteClockInitialTime = Timestamp::Millis(373);
26 constexpr uint32_t kTimestampOffset = 567;
27 constexpr int64_t kRemoteToLocalClockOffsetNtp =
28 ToNtpUnits(kLocalClockInitialTime - kRemoteClockInitialTime);
29
30 class RemoteNtpTimeEstimatorTest : public ::testing::Test {
31 protected:
AdvanceTime(TimeDelta delta)32 void AdvanceTime(TimeDelta delta) {
33 local_clock_.AdvanceTime(delta);
34 remote_clock_.AdvanceTime(delta);
35 }
36
GetRemoteTimestamp()37 uint32_t GetRemoteTimestamp() {
38 return static_cast<uint32_t>(remote_clock_.TimeInMilliseconds()) * 90 +
39 kTimestampOffset;
40 }
41
SendRtcpSr()42 void SendRtcpSr() {
43 uint32_t rtcp_timestamp = GetRemoteTimestamp();
44 NtpTime ntp = remote_clock_.CurrentNtpTime();
45
46 AdvanceTime(kTestRtt / 2);
47 RTC_DCHECK(estimator_.UpdateRtcpTimestamp(kTestRtt, ntp, rtcp_timestamp));
48 }
49
SendRtcpSrInaccurately(TimeDelta ntp_error,TimeDelta networking_delay)50 void SendRtcpSrInaccurately(TimeDelta ntp_error, TimeDelta networking_delay) {
51 uint32_t rtcp_timestamp = GetRemoteTimestamp();
52 int64_t ntp_error_fractions = ToNtpUnits(ntp_error);
53 NtpTime ntp(static_cast<uint64_t>(remote_clock_.CurrentNtpTime()) +
54 ntp_error_fractions);
55 AdvanceTime(kTestRtt / 2 + networking_delay);
56 RTC_DCHECK(estimator_.UpdateRtcpTimestamp(kTestRtt, ntp, rtcp_timestamp));
57 }
58
59 SimulatedClock local_clock_{kLocalClockInitialTime};
60 SimulatedClock remote_clock_{kRemoteClockInitialTime};
61 RemoteNtpTimeEstimator estimator_{&local_clock_};
62 };
63
TEST_F(RemoteNtpTimeEstimatorTest,FailsWithoutValidNtpTime)64 TEST_F(RemoteNtpTimeEstimatorTest, FailsWithoutValidNtpTime) {
65 EXPECT_FALSE(
66 estimator_.UpdateRtcpTimestamp(kTestRtt, NtpTime(), /*rtp_timestamp=*/0));
67 }
68
TEST_F(RemoteNtpTimeEstimatorTest,Estimate)69 TEST_F(RemoteNtpTimeEstimatorTest, Estimate) {
70 // Remote peer sends first RTCP SR.
71 SendRtcpSr();
72
73 // Remote sends a RTP packet.
74 AdvanceTime(TimeDelta::Millis(15));
75 uint32_t rtp_timestamp = GetRemoteTimestamp();
76 int64_t capture_ntp_time_ms = local_clock_.CurrentNtpInMilliseconds();
77
78 // Local peer needs at least 2 RTCP SR to calculate the capture time.
79 const int64_t kNotEnoughRtcpSr = -1;
80 EXPECT_EQ(kNotEnoughRtcpSr, estimator_.Estimate(rtp_timestamp));
81 EXPECT_EQ(estimator_.EstimateRemoteToLocalClockOffset(), absl::nullopt);
82
83 AdvanceTime(TimeDelta::Millis(800));
84 // Remote sends second RTCP SR.
85 SendRtcpSr();
86
87 // Local peer gets enough RTCP SR to calculate the capture time.
88 EXPECT_EQ(capture_ntp_time_ms, estimator_.Estimate(rtp_timestamp));
89 EXPECT_EQ(estimator_.EstimateRemoteToLocalClockOffset(),
90 kRemoteToLocalClockOffsetNtp);
91 }
92
TEST_F(RemoteNtpTimeEstimatorTest,AveragesErrorsOut)93 TEST_F(RemoteNtpTimeEstimatorTest, AveragesErrorsOut) {
94 // Remote peer sends first 10 RTCP SR without errors.
95 for (int i = 0; i < 10; ++i) {
96 AdvanceTime(TimeDelta::Seconds(1));
97 SendRtcpSr();
98 }
99
100 AdvanceTime(TimeDelta::Millis(150));
101 uint32_t rtp_timestamp = GetRemoteTimestamp();
102 int64_t capture_ntp_time_ms = local_clock_.CurrentNtpInMilliseconds();
103 // Local peer gets enough RTCP SR to calculate the capture time.
104 EXPECT_EQ(capture_ntp_time_ms, estimator_.Estimate(rtp_timestamp));
105 EXPECT_EQ(kRemoteToLocalClockOffsetNtp,
106 estimator_.EstimateRemoteToLocalClockOffset());
107
108 // Remote sends corrupted RTCP SRs
109 AdvanceTime(TimeDelta::Seconds(1));
110 SendRtcpSrInaccurately(/*ntp_error=*/TimeDelta::Millis(2),
111 /*networking_delay=*/TimeDelta::Millis(-1));
112 AdvanceTime(TimeDelta::Seconds(1));
113 SendRtcpSrInaccurately(/*ntp_error=*/TimeDelta::Millis(-2),
114 /*networking_delay=*/TimeDelta::Millis(1));
115
116 // New RTP packet to estimate timestamp.
117 AdvanceTime(TimeDelta::Millis(150));
118 rtp_timestamp = GetRemoteTimestamp();
119 capture_ntp_time_ms = local_clock_.CurrentNtpInMilliseconds();
120
121 // Errors should be averaged out.
122 EXPECT_EQ(capture_ntp_time_ms, estimator_.Estimate(rtp_timestamp));
123 EXPECT_EQ(kRemoteToLocalClockOffsetNtp,
124 estimator_.EstimateRemoteToLocalClockOffset());
125 }
126
127 } // namespace
128 } // namespace webrtc
129